Passing string as function variable for renaming table column

I am trying to pass a string variable to a custom function to rename a table column title.

My code is below:

temperature = 'OPC.Temperature.BottomTemperature';
temp_column_name = 'Temperature';

%extract bottom temperature data
data_temp = dataextract(data_temp,temperature,temp_column_name);

Below is the function:

function [ data ] = dataextract( data_array,variable,column_name )
    %remove all rows not containing variable in column 2
    data_string = variable;
    data_comp = strcmp(data_array(:,2),data_string);
    data_comp = ~data_comp;
    data_array(data_comp,:) = [];

      %remove extra information from columns 3 & 4 from data array
      data_array(:,(2:4)) = [];

      %convert data_array cell array to table
      data_array = array2table(data_array,'VariableNames',{'TimeStamp', column_name});

      %convert timestamp string to datetime
      data_array.TimeStamp = datetime(data_array.TimeStamp,'InputFormat','yyyy-MM-dd HH:mm:ss.SSS');

      %convert beam current string to double precision value
      data_array.column_name = str2double(data_array.column_name);

      data = data_array;
  end

I tried to initially just pass 'Temperature' in the function but that would not work and now a variable won't pass either. Below is my error:

Error using dataextract (line 18)
Unrecognized variable name 'column_name'.

Error in parser_test (line 38)
data_temp = dataextract(data_temp,temperature,temp_column_name);

Answer 1

[Walter Roberson]

Change

        data_array.column_name = str2double(data_array.column_name);

to

        data_array.column_name = str2double(data_array.(column_name));

[jcledfo2]

Thanks!!

I had to also add () to the beginning or it added an extra column

          data_array.(column_name) = str2double(data_array.(column_name));